Means and process for the amplification of radiant energy



June 17, 1930. J. J. DALEY 1,764,934

MEANS AND PROCESS FOR THE AMPLIFICATION 0F RADIANT ENERGY Original Filed (JG-h. 24, 1927 Patented June 17, 1930 UNITED STATES 7 REISSUEB PATENT OFFICE JOSEPH J. DALEY, OF BOSTON, MASSACHUSETTS, ASSIGN'OR TO WALTER M. GUSICK,

OF BOSTON, MASSACHUSETTS I MEANS AND PROCESS FOR THE AMPLIFICATION 0F RADIANT ENERGY Original application filed October 24, 1927, Serial No. 228,249. Divided and this application filed April 26, 1930. Serial No. 447,715.

tive and less selective; while the method depending'upon the production of an opposing current not only reduced the overall efficiency of the amplifier, but was in itself effective only over a very limited range of frequency.

Heretofore all systems of reception and amplification of radiant energy were built around the conception that these disturbing currents and their consQuent oscillations were inevitable. Certain systems sought to force these oscillations further to produce aform of amplification in connection with the detector tube but this gave rise to very serious distortion and undesirable noises. When true amplification at high frequencies was attempted these oscillations, as stated above, became the limiting factor and had to be damped and suppressed before any appreciable degree of amplification could be obtained. It has been found that when these undesired oscillatory currents have been suppressed to ,a degree that permits of reasonable amplification, the desired and useful oscillatory currents in the circuit have also been suppressed to a Very considerable degree, thus reducing the efficiency of the entire circuit.

I have found that between the zone of forced oscillations and the zone of damped oscillations there exists a critical point at which there is nofiow of disturbing current and consequently no undesired oscillations. In my invention I have brought about this condition of true non-regeneration, never before realized, by a novel arrangement of inductances and capacities which in themselves constitute the amplifier circuit. This condition of true non-regeneration is preferably obtained by selection of values which will produce a zero difference of potential in respect to all undesired currents between the elements, such as grid and plate, of the electronic device at any desired frequency. The electrical relation of the various parts ofthe circuit is such that this condition of true non-regeneration is automatically maintained for any desired frequency; and since no undesired oscillations can now exist, all necessity for their suppression has been eliminated. This novel arrangement of inductances and capacities more specifically described below produces a higher degree of amplification per stage than has stable operation in an amplifier may be present even when the undesired oscillatory currents are not present. This condition is brought about by the flow of currents, desirable in themselves, in a path where they do not belong. In other words, to obtain a high degree of efiiciency in amplification without distortion, the circuit must contain only the useful and desirable currents and their flow must be restricted to their proper and useful paths. The means by which I accomplish this object are described in detail below.

Thus this invention makes possible full and eflicient amplification at any desired frequency and equal amplification at all frequencies without disturbing currents.

Since the energy transfer due to electromagnetic coupling increases with an increase of frequency, and since the magnetic coupling remains constant at its optimum value, the point is quickly reached at which means of electrostatic coupling simultaneously. The value of energy transfer through static coupling is not a function of frequency, and if the value of the static coupling were constant, the combination of magnetic and static coupling must still vary with frequency in approximately a straight line ratio. If the value of the static coupling could be made to vary coincidentally with changes in received frequency but in the inverse ratio, the combination of magnetic and static coupling could be made to produce, by a proper selection of values, the maximum transfer of energy without permitting at any time the existence of disturbing currents which produce uncontrolled oscillation in the tube.

In this invention, the direct means used to create static coupling is a capacity connecting the primary and secondary windings of the radio frequency transformer. This capacity, however, is also in series with the tuning condenser, and therefore the real value of the static leg of this system must be represented by the values of the two capacities in series, which would be mathematically speaking the value of one over the sum of their reciprocals. In other words,

In this electrostatic leg, the tuning con denser is to the coupling condenser in about the ratio of 1 to 20, and is variable. Therefore, as the system is tuned to a higher frequency, the value of the tuning condenser is reduced, thereby reducing the entire value of the static coupling to compensate for the increase in value of magnetic coupling due to increased frequency. Conversely, as frequency decreases, the increase in value of the tuning condenser, and therefore of the Whole static leg, compensates for the decreased value of the magnetic leg for the lower frequency.

The determination of the values of the two capacities must be made mathematically by following the formula the change in the total capacity (C will be inversely proportional to the change in value of the magnetic coupling due to change of frequency.

When the proper values have been obtained, the act of tuning will automatically maintain the proper balance between the electromagnetic and electrostatic legs, thus maintaining the maximum energy transfer at all frequencies, and preventing the production of any disturbing currents to cause undesired oscillation.

In addition, all other undesired currents are excluded from the circuits, and all undesired transfers of energy from one part of the circuit to another is' eliminated by means of choke coils and condensers as shown hereinafter.

The inductances used in the magnetic leg of this amplifier circuit take the form of transformers. I have found as a result of a long series of experiments that the introduction of a direct current into the primary of such a transformer is extremely detrimental. The radio currents impressed upon the primary of such a transformer are necessarily of a very low intensit and are modulated for example by voice requencies, music or other modulating frequencies. It is desired that the current induced in the secondary winding of the transformer retain without an change the modulation characteristics 0 the original current although there may have been a certain definite increase in voltage. If any direct current is allowed to flow in the primary coil, the magnetic field intensity is inevitably increased. This field intensity may increase until its results are comparable to the phenomenon known as core saturation in iron core transformers. Its effect is to dampen or suppress the fine variations of the modulated current, in fact it may entirely eliminate some of the weaker modulations. As a result of this, the current induced in the secondary of a transformer in which direct current is allowed to flow in the primary, does not contain a true reproduction of the modulations existing in the radio current originally impressed on the primary.

Since these modulations represent and are produced by the original voice, music, etc., and on them, after rectification, depends the reproduction of that voice or music, it is obvious that if they are changed or suppressed or eliminated to any degree in transit, the resulting reproduction must be untrue and distorted. To meet this condition I have introduced into the plate circuit a capacity so arranged as to prevent all direct current from flowing into the primary of the transformers, but at the same time, permitting free flow of the modulated pulsating radio frequency current into the said primaries.

It must be noted that the interposition of such a capacity will result in a change of phase in the current flowing in the primary of the transformer so therefore I reverse the direction of the winding of the primary coil in order that the current in it may be again restored to proper phase.

When direct current is allowed to flow in the primary of the transformers the resulting intensification of the magnetic flux also greatly enlarges the external field of the coil. Thus it becomes increasingly difficult to prevent undesired energy transfer through inter-stage coupling. If shielding is used the shields for each stage must be made so large as to be unpracticable, otherwise the entire efliciency of the amplifier is greatly reduced as a result of the large eddy currents set up. By eliminating all direct current from \the transformers, as I have done in my invention, the external field is so reduced that small close shields'may be used and all inter-stage coupling removed. In fact the external field is so small that in many instances shielding may be dispensed with.

I have also found that the voltage drop across the high resistance of the common source of plate current supply created by the passage of the pulsating current flowing back from the plate may effect a coupling between stages or a feed back to the grid circuit. I have placed choke coils of such values and in such a position in the plate circuit of each stage and thereby eliminated entirely this very detrimental effect.

The drawing forming part of this specification illustrates in diagram the circuits embodying my invention. The drawing shows two stages of radio frequency amplification although the invention is not restricted to that number. One is in the antenna circuit and each stage consists preferably of an air core radio frequency trans former havin a minimum of dielectric losses, of which 1 is the primary and 2 is the secondary. This transformer is tuned by two condensers or other capacities, one of which, 3, is variable, and 4 is fixed; the condenser 4 being in series connection electrically with the condenser 3, and both bein in shunt connection across the terminals 0 the secondary coil 2, thus making the combination of capacities 3 and 4 variable when 3 is varied. The circuit also contains an electronic tube having grid 5, plate 6 and filament 7.

The filament 7 is connected to its battery in the usual manner, and has in its circuit a suitable resistance 8, preferably in the negative side to maintain the proper operating condition. The grid 5 is connected to one end of the secondary coil 2; the other end of the secondary constituting the grid return being connected into the negativeside of the filament circuit at a point between the resistance 8 and the battery.

The plate 6 is connected to its battery through a ra io frequenc choke coil 9,

and to the primary 1 of the next following radio frequency transformer through a condenser 10.

In this way, while the direct component of the plate battery may pass readily to the plate 6 through the choke 9, it can never flow into the primary 1 of the radio frequency transformer because of the interposition of the condenser 10. On the other hand, the electromagnetic component on the plate being of a modulated pulsating nature will flow readily into the primary coil 1 through the condenser 10 where it is desired, but is efiectively checked from flowing further into the plate battery circuit or through it into ad acent stages of amplification where it is not desired, by the interposition of the choke 9. The primary coil 1 has its one end connected to the plate of the preceding tube through the condenser 10, or to the antenna in the case of the first stage, and its other end connected to the common connector between the rotor plates of the variable condenser 3 and one side of the fixed condenser 4.

Thus the variations in the electromagnetic side (the coils 1, 2) due to change of frequency are compensated for in the electrostatic side which is made up of the condensers 3 and 4, since there exists between the primary 1 and the secondary 2 not only magnetic coupling but also static coupling through the condenser 4 which is itself in series with. the condenser 3, and variable with it.

It is essential for the operation of this circuit that the coil 1 be always in phase with the coil 2, and since the condenser 10 serves to reverse the phase of the input to the following primary 1, this primary must be in itself reversed in phase so that the resulting current is once more brought into proper phase-with the current in the 0011 2.

What I claim is:

1. A system of amplification of radiant energy comprising electromagnetic and electrostatic paths of energy transfer and an electronic device wherein the electromagnetic and the electrostatic values of said transfer paths are balanced to produce a zero difference of potential in respect to all undesired currents between the elements of the electronic device and to obtain a substantially equal energy transfer throughout the range of frequencies to which the system is tunable.

2. A system of amplification of radiant energy comprising electromagnetic and electrostatic paths of energy transfer and an electronic device wherein the electromagnetic and the electrostatic values of said transfer paths are balanced to produce a zero difference of potential in respect to all undesired currents between the grid and plate of the electronic device and to obta n 4. A system of amplification of radiant energy as set forth in claim 3 which provides capacities to form an electrostatic path of energy transfer whose value is definitely variable, and inductances comprising a transformer to form an electromagnetic path whose value is naturally variable with changes of frequency; the electrical relationship of these two paths and their values being such that a maximum transfer of energy is obtained without regeneration or any flow of undesirable disturbing currents at any desired frequency.

5. A system of amplification of radiant energy as set forth in claim 3 combined with another stage of amplification, the plate of the preceding electronic device being connected to the primary of the following transformer through a capacity for the purpose of preventing the flow of direct current in the primary of the transformer, but permitting the free flow of the modulated alternating currents from the plate through the primary of the transformer and said plate being connected to its source of direct current through a choke coil placed in series between the plate and the source of direct current for the purpose of preventing the flow of alternating current back through the source of direct current supply, but permitting the fiow of direct current from its source to the plate.

6. A system of Timplification of radiant energy as set forth in claim 3 combined with one or more other stages, each of said other stages having a capacity of suitable value connected in series between the plate of the preceding electronic device and the primary of the transformer of such stage, and having a suitable source of direct current con nected in shunt to a point in the circuit between said plate and the above-mentioned capacity, and having a choke coil of suitable value interposed in seriesin the above-mentioned shunt between the source of direct current-and the plate, for the purpose of separating the current on the plate into two components, one of which is a modulated alternating component which is allowed to pass freely into the primary of the transformer of such stage but is not allowed to flow back through the common source of direct current supply, the other component being a direct current component which is allowed to pass freely from the direct current source to the plate, but is not allowed to flow over into the primary of the transformer of such stage.

7. A system of amplification of radiant energy as set forth in claim 3 which comprises an electromagnetic and an electrostatic path of energy transfer whose values are variable, automatically, by the act of tuning, said values being so related to each other as to produce a zero difference of potential in respect to all undesired currents between the grid and plate of the electronic device when the set is tuned to any given frequency.

8. A system of amplification of radiant energy comprising an electronic device, a transformer, a tuning capacity, a capacity connected in series between the primary and secondary of said transformer, said capacity being also in series with the tuning capacity and both capacities being connected in shunt across the secondary of the transformer, and the electrical values of said inductanccs and capacities being so selected and so related to each other as to simultaneously maintain a condition of complete non-regeneration and a condition of energy transfer maintained constant at its maximum value at any desired frequency.

9. A system of amplification of radiant energy comprising an electronic device having an output circuit which comprises a transformer, a variable condenser, and. a series' condenser, said variable and series condensers being connected in series with each other and the two being connected in shunt across the secondary of said transformer and one end of the primary of said transformer being connected into the series connection between the two said condenscrs and their values being selected so as to prevent the production of undesired disturbing oscillations in the electronic device.

10. In a system of amplification of radiant energy comprising an electronic device, a transformer, a tuning capacity, a capacity connected in series between the primary and secondary of said transformer, said capaclty being also in series with the tuning capacity, and both capacities being connected in shunt across the secondary of the transformer, the process of simultaneously maintaining a condition of complete non-regeneration and a condition of energy transfer maintained constant at its maximum value over any desired range of frequency by the selection and relation of the electrical values of said inducttances and capacities.

11. In a system of amplification of radiant energy comprising an electronic device, a

transformer, a tuning capacity, a capacity connected in series between the primary and secondary of said transformer, said capacity being also in series with the tuning capacity, and both capacities being connected in shunt across the secondary of the transformer, said capacities providing an electrostatic coupling and said inductances providing an electromagnetic coupling, the process consisting in automatically varying the energy transfer through the electrostatic coupling as the tuning capacity is varied and to such a degree as to compensate for the natural change of energy transfer in the electromagnetic coupling arising from change of frequency, thereby effecting a condition of energy transfer maintained constant at its max imum value for any desired range of frequency and thereby simultaneously maintaining a condition of complete honregenera tion.

12. In a system of amplification of radiant energy comprising an electronic device, a transformer, a tuning capacity, a capacity connected in series between the primary and secondary of said transformer, said capacity being also in series with the tuning capacity, and both capacities being connected in shunt across the secondary of the transformer, said capacities providing a static coupling and said inductances providing a magnetic coupling, the process consisting in automatically varying the energy transfer through the static coupling as the tuning capacity is varied and to such a degree as to compensate for the natural change of energy transfer in the magnetic coupling arising from a change of frequency but in the inverse'rat-io thereby simultaneously maintaining a condition of complete non-regeneration and a condition of energy transfer maintained constant at its maxlmum value at any desired frequency.

JosEPH J. DALEY. 

